Silver recovery device

ABSTRACT

A cylindrical electrolysis tank (10) whose inner wall surface (11c) is held in contact with a single-use cathode (30) defining a hollow cylinder is provided with a removable tank lid (14) which forms an integral unit with a hollow cylinder (16) which carries the anode (34) on its peripheral surface (16a) and is provided with an uninterrupted closed bottom plate (17). The cylinder space (24) which is freely accessible from above serves to accommodate a replacement cathode (30) which is rolled up. At the circumferential abutment edge (18) between the peripheral surface (16a) of hollow cylinder (16) and the inner surface (19a) of lid plate (19) a ventilation groove (20) is provided which has a bore (20a) including an air-exhaust valve (21) and extending to the exterior.

The invention relates to a device for electrolytically recovering silverfrom a photographic processing fluid, said device comprising acylindrical electrolysis tank with a fluid supply pipe and a fluiddischarge pipe arranged in its bottom as well as a removable tank lidincluding a ventilation means, a hollow-cylindrical anode arrangedconcentrically within the cylindrical tank, a single-use cathode in theform of a hollow cylinder which rests against the inner surface of thetank wall as well as electric connections for the cathode and the anode.

DE-PS 40 07 906 discloses a device of this type in which the anodeextending into the electrolysis tank is screwed to the tank lid.

The anode consists of a plastic cylinder and a holding bracket. Theouter surface of the cylinder as well as the inner surface of theholding bracket are covered by an adhesively attached graphite foil. Thebracket is screwed to the cylinder such that the graphite surfaces reston each other and form an electric contact. By means of two furtherscrews the bracket together with the cylinder is attached to the innersurface of the lid. The attachment screws which extend through the lidalso serve as connections to the outside power supply.

This arrangement is disadvantageous in that the tank lid and the anodearrangement consist of a plurality of parts which are screwed togetherand whose assembly is very time-consuming.

It is the object of the invention to provide a tank lid and an anodearrangement which consists of a small number of parts, which is easy tomanufacture and whose assembly requires a minimum of operations.

According to the invention this object is attained in that the tank lidforms an integral unit with a hollow cylinder which extends into theelectrolysis tank from above and carries the anode on its peripheralsurface.

According to an advantageous modification the hollow cylinder has aclosed bottom plate and defines a cylinder space which is freelyaccessible from above.

The advantage attainable by the invention consists in that the tank lidand the anode holder form one single component which can be made in onestep. Moreover the current is homogeneously distributed between cathodeand anode within the electrolytic cell.

The invention will be described with reference to an embodimentschematically illustrated in the drawing.

The single FIGURE shows a lateral sectional view of a silver recoverydevice of substantially the same design as that proposed in DE-PS 40 07906. Therefore the description of the subject matter of the inventionwith reference to the FIGURE only deals with those parts as contributingto a better understanding of the invention.

The cylindrical plastic electrolysis tank generally denoted 10 isprovided with a fixedly arranged bottom plate 12 and a removable tanklid 14. The marginal area of bottom plate 12 features noses 13 and themarginal area of the lower side of the lid noses 15, which extend intotank 10 and rest against the inner surface 11c of tank wall 11. Thenoses serve to hold a cylindrical single-use cathode 30 of the typedescribed in the above-mentioned DE-PS 40 07 906 in contact with theinner surface 11c of tank wall 11.

Moreover two clamping bolts 25 are provided by means of which electriccontact is made with the single-use cathode provided with the negativecable, said cathode being thus additionally held.

A fluid discharge pipe 28 is arranged in the center of bottom plate 12and a fluid supply pipe 26 at any suitable point of the range of bottomplate 12 between an anode 34 and the cathode 30. Inserted into saiddischarge pipe is an upright tube 27 which is provided with nozzles 27aand sealed by a cover.

The tank lid 14 according to the invention which includes an areaupwardly inclined at a slight angle or having a slight upward curvatureforms an integral unit with a hollow cylinder 16 which extends downwardsinto the electrolysis tank 10. Anode 34 which consists of a thin foil 35coated with carbon is bonded to its peripheral surface 16a. The hollowcylinder 16 is closed by a bottom plate 17 and defines a cylinder space24 freely accessible from above. On half the level of the cylinderspace, two oppositely arranged threaded buttonhead bolts 23 are providedwhich extend through the cylinder wall and the carbon foil 35 of anode34. The bolt ends projecting into the cylinder space 24 are connectedwith the positive cable 22 for the electric power supply. The cable endsare each clamped between two nuts screwed onto the threaded bolts 23.O-rings (not illustrated) placed on the threaded bolts between the nutsand the wall of the hollow cylinder 16 serve as sealing members.

At the circumferential abutment edge 18 between the peripheral surface16a of hollow cylinder 16 and the inner surface 19a of the circular lidplate 19, a circumferential ventilation groove 20 is provided in theinner surface 19a, said groove having a pretermined depth on one sideand rising on either side such that it terminates in the inner surface19a of circular lid plate 19 on the diametrically opposite side. As canbe seen from the FIGURE, a bore 20a, into which an air-exhaust valve 21is inserted, extends from the deepest level of ventilation groove 20 tothe exterior.

As was described above, the tank lid and the anode holder form anintegral unit which can be manufactured rapidly and without problem witha minimum of material in one single operation, for example by means ofan extrusion molding process. Moreover, in the free space 24 of hollowcylinder 16, which is accessible from outside, a cylindrical single-usereplacement cathode 30 may be deposited. In addition, when lid 14 islifted during opening of the electrolysis tank the fluid level islowered in proportion to the volume of the hollow cylinder 16 closed bybottom plate 17 so that there is no danger of fluid overflowing andbeing spilled respectively.

I claim:
 1. Device for electrolytically recovering silver from aphotographic processing fluid, said device comprising a cylindricalelectrolysis tank with a removable lid including a ventilation means, abottom and cylindrical walls having an inner surface surrounding thebottom, said bottom being provided with a fluid supply pipe and a fluiddischarge pipe arranged therein, a hollow-cylindrical anode arrangedconcentrically within the tank, a single-use cathode in the form of afirst hollow cylinder which rests against the inner surface of thewalls, and electrical connections for the cathode and anode,characterized in that the tank lid forms an integral unit with a secondhollow cylinder which extends downwards into the electrolysis tank, saidsecond hollow cylinder having a peripheral surface, and wherein saidanode being mounted on said peripheral surface.
 2. Device according toclaim 1, characterized in that said second hollow cylinder (16)comprises a closed bottom plate (17) and defines a cylinder space (24)which is freely accessible from above.
 3. Device according to claim 1,characterized in that a bolt is mounted in opposite walls of said secondhollow cylinder, said bolts each having an end portion that extendsthrough said respective wall, into and through the carbon foil of saidanode and terminates in the second hollow cylinder, each said endportion terminating in said second hollow cylinder provide a connectionfor positive cable from an electric power supply.
 4. Device according toclaim 1, characterized in that said tank lid comprises a circular lidplate, said circular lid plate having an inner surface.
 5. Deviceaccording to claim 4 characterized in that a circumferential abutmentedge is defined between said peripheral surface of said second hollowcylinder and the inner surface of said circular lid plate.
 6. Deviceaccording to claim 5, characterized in that a circumferentialventilation groove is provided in said inner surface.
 7. Deviceaccording to claim 6, characterized in that said ventilation groove (20)has a predetermined depth on one side and rises on either side such thatit terminates in the inner surface (19a) of the circular lid plate (19)on the diametrically opposite side.
 8. Device according to claim 7,characterized in that a bore (20a), into which an air-exhaust valve (21)is inserted, extends from the deepest level of the ventilation groove(20) to the exterior.
 9. Device according to claim 6, characterized inthat a bore (20a), into which an air-exhaust valve (21) is inserted,extends from the deepest level of the ventilation groove (20) to theexterior.
 10. Device according to claim 1, characterized in that saidanode consist of carbon foil.